Many of the country's biggest chains and their online sites have already run out of the healthy superfood while remaining stocks are fast disappearing.
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And the shortage is likely to go on for as long as three weeks after crops were washed out by storms in Spain, the main supply region for Popeye's favourite food during the winter months.
Posh Waitrose reports stocks have run out in many stores and have put up notices warning the shortages could last for three weeks.
Meanwhile consumers posted on social media that they were finding all their local stores had sold out of spinach, with many assuming it was because of January health kicks.
But the real reason for the shortage is a series of storms in the Murcia region of Spain which has suffered its heaviest rainfall in 30 years.
The area supplies around 80 per cent of Britain's spinach during the winter months, said trade journal The Grocer.
The Leafy Salad Growers' Association said: "Rainfall left some fields reduced to just 30 per cent capacity after receiving between 150 to 250 litres of water per square metre.
"Spinach is like gold dust here in the UK."
It has been made worse by 'unseasonably' cold weather in Greece and Italy who also supply some stocks during this time of year.
The Association added: "Shoppers will notice that supermarkets will begin to run out of spinach in the coming days if they haven't already so it's time to turn to another leaf for now."